Nutritional studies often address multiple independent and dependent variables and do not, or are not able to, distinguish which factors lead to which results. Thus, a perplexing and incomplete picture has emerged for many aspects of nutritional management for which nurses have responsibility. There is little evidence that a knowledge base is being systematic built for nurses to use for making decisions to promote optimal nutritional delivery for patients. This is particularly true for patients receiving enteral feedings. Enteral feeding implies delivery of food by tube into the stomach or small intestine. In preparation for evaluating physiologic responses to enteral feedings, this 3-year, small scale study proposes use of a well-established animal model (rat) to examine the effects of varying a) food consistency [solid and liquid], b) time for access to food [24 hr and 12 hr], c) kilocalorie (kcal) level [80 and 55], and d) fiber content of oral feedings on systemic and gut-specific responses. The specific aims of the study are to characterize and compare daily temporal patterns for the systematic responses of plasma corticosterone and insulin levels and to examine gut structural and functional integrity among adult rats with two different food consistencies, two times for access to food, two kcal levels, and two fiber contents. A prospective, experimental 2 x 2 x 2 x 2, randomized post-test only design is the research approach of choice, with an examination of 12 cells in the 16 cell design. The four cells not used are those for solid food with low fiber. Young adult male rats will be entered into this 21-day study after 7 days acclimation to the laboratory environment. There will be five rats in each of the 12 cells for the two dependent variables of plasma corticosterone and gut structural integrity (n=60). A second set of 60 rats (5/cell) will be used for the dependent variables of plasma insulin and gut functional integrity. Hourly blood draws over 48 hours are planned for study days 19 and 20. Ten (10) samples of 0.2ml each will be withdrawn from each rat through a surgically implanted vascular catheter. On day 21, tissues for measuring gut structural or gut functional integrity will be obtained. Structural integrity aspects include intestinal segment mucosal and serosal weights, protein and deoxyribonucleic acid (DNA) contents, and histologic features. Functional integrity aspects include segment cross-sectional and circular muscle contractility, body weights, and weights of a standardized skeletal muscle section and selected organs. Composite structural and functional integrity indexes will be generated and used in analyses. Quantitative analyses will focus on data from each separate treatment group as well as data comparisons among treatment groups using analysis of variance (ANOVA). To characterize temporal patterns in plasma levels, cosinor analysis is planned. The results will serve as a basis for future study of enteral feedings which are often delivered to patients using different schedules, kcal levels, and fiber contents.